US6400799B1 - X-ray tube cooling system - Google Patents

X-ray tube cooling system Download PDF

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Publication number
US6400799B1
US6400799B1 US09/351,579 US35157999A US6400799B1 US 6400799 B1 US6400799 B1 US 6400799B1 US 35157999 A US35157999 A US 35157999A US 6400799 B1 US6400799 B1 US 6400799B1
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Prior art keywords
coolant
ray tube
shield structure
shield
fluid
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US09/351,579
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English (en)
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Gregory C. Andrews
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Varex Imaging Corp
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Varian Medical Systems Inc
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Priority to US09/351,579 priority Critical patent/US6400799B1/en
Assigned to VARIAN MEDICAL SYSTEMS, INC. reassignment VARIAN MEDICAL SYSTEMS, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ANDREWS, GREGORY C.
Priority to PCT/US2000/018796 priority patent/WO2001005196A2/en
Priority to DE60045160T priority patent/DE60045160D1/de
Priority to EP00948608A priority patent/EP1234320B1/en
Priority to JP2001510277A priority patent/JP4376480B2/ja
Priority to US09/656,076 priority patent/US6519318B1/en
Application granted granted Critical
Publication of US6400799B1 publication Critical patent/US6400799B1/en
Assigned to VARIAN MEDICAL SYSTEMS TECHNOLOGIES, INC. reassignment VARIAN MEDICAL SYSTEMS TECHNOLOGIES, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: VARIAN MEDICAL SYSTEMS, INC.
Priority to JP2008248952A priority patent/JP4749456B2/ja
Assigned to VARIAN MEDICAL SYSTEMS, INC. reassignment VARIAN MEDICAL SYSTEMS, INC. MERGER (SEE DOCUMENT FOR DETAILS). Assignors: VARIAN MEDICAL SYSTEMS TECHNOLOGIES, INC.
Assigned to VAREX IMAGING CORPORATION reassignment VAREX IMAGING CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: VARIAN MEDICAL SYSTEMS, INC.
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/16—Vessels; Containers; Shields associated therewith
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/02—Constructional details
    • H05G1/025—Means for cooling the X-ray tube or the generator
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/02—Constructional details
    • H05G1/04—Mounting the X-ray tube within a closed housing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/12—Cooling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/12—Cooling
    • H01J2235/1225—Cooling characterised by method
    • H01J2235/1262—Circulating fluids
    • H01J2235/1283—Circulating fluids in conjunction with extended surfaces (e.g. fins or ridges)
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/16—Vessels
    • H01J2235/165—Shielding arrangements
    • H01J2235/168—Shielding arrangements against charged particles

Definitions

  • the present invention relates generally to x-ray tubes. More particularly, embodiments of the present invention relate to an x-ray tube cooling system that increases the rate of heat transfer from the x-ray tube to a cooling system medium, thereby significantly reducing heat-induced stress and strain in x-ray tube structures and extending the operating life of the device.
  • X-ray producing devices are extremely valuable tools that are used in a wide variety of applications, both industrial and medical.
  • such equipment is commonly used in areas such as diagnostic and therapeutic radiology; semiconductor manufacture and fabrication; and materials analysis and testing.
  • x-rays While used in a number of different applications, the basic operation of x-ray devices is similar. In general, x-rays, or x-ray radiation, are produced when electrons are produced and released, accelerated, and then stopped abruptly.
  • the basic typical x-ray tube has a cathode cylinder with an electron generator, or cathode, at one end. Electrical power applied to a filament portion of the cathode generates electrons by thermionic emission.
  • a target anode is axially spaced apart from the cathode, and is oriented so as to receive electrons emitted by the cathode.
  • a voltage source that is used to apply a high voltage potential between the cathode and the anode.
  • the high voltage potential is applied between the cathode and the anode, which causes the thermionically emitted electrons to accelerate away from the cathode and towards the anode in an electron stream.
  • the accelerating electrons then strike the target anode surface (or focal track) at a high velocity.
  • the target surface on the anode is composed of a material having a high atomic number, and a portion of the kinetic energy of the striking electron stream is thereby converted to electromagnetic waves of very high frequency, i.e., x-rays.
  • the resulting x-rays emanate from the target surface, and are then collimated through a window formed in the x-ray device for penetration into an object, such as a patient's body.
  • the x-rays that pass through the object can be detected and analyzed so as to be used in any one of a number of applications, such as x-ray medical diagnostic examination or material analysis procedures.
  • a percentage of the electrons that strike the anode target surface do not generate x-rays, and instead simply rebound from the surface. These are often referred to as “back-scatter” electrons.
  • some of these rebounding electrons still traveling at relatively high velocities—are blocked and collected by a shield structure that is positioned between the cathode and the anode so they do not re-strike the target surface of the anode. This prevents the rebounding electrons from re-impacting the target anode and producing “off-focus” x-rays, which can negatively affect the quality of the x-ray image.
  • Some of the rebounding electrons may also impact the interior of the cathode cylinder.
  • the heat produced is not evenly distributed.
  • the different heat regions result in varying rates of thermal expansion, resulting in mechanical stresses that can also damage the x-ray tube device, especially over numerous operating cycles.
  • mechanical stress and strain is induced when the cooler part of the structure resists the expansion of the hotter portion of the structure.
  • the level of stress and strain is relatively insignificant at low temperature differentials.
  • non-uniform expansion produced by high temperature differentials induces destructive mechanical stresses and strains that can ultimately cause a mechanical failure in the part.
  • these stresses are especially damaging to joints between attached components.
  • x-ray tubes In order to dissipate the high heat present, x-ray tubes have typically utilized some type of liquid cooling arrangement. In such systems, at least some of the external surfaces of the cathode cylinder are placed in direct contact with a circulating coolant, which facilitates a convective cooling process. Often however, this approach is not satisfactory for cooling an adjacent shield structure, which has a limited external surface area, and, because it is exposed to extremely high temperatures from rebounding electrons, is unable to efficiently transfer significant amounts of heat by convection to the coolant. To address this problem, shield structures have been fashioned with internal cooling passages through which a coolant stream is circulated. Thus, the shield structure gives up heat primarily by convection to the coolant which flows through its interior. This approach has not been entirely satisfactory either.
  • x-ray devices of this sort may experience greater failure rates and shorter operating lives due to repeated exposure to higher temperatures and resultant stresses.
  • the coolant must be capable of absorbing significant amounts of heat in order to preclude harmful thermal stresses and strain in the shield structure and cathode cylinder.
  • the circulated coolant eventually, and often prematurely, experiences thermal breakdown and is no longer able to effectively remove heat from the x-ray tube. Again, this translates into an x-ray device that is more subject to failure and that typically has an overall shorter operating life.
  • the cathode cylinder is fashioned as a single integral part that must be attached to the shield structure.
  • the shield structure is then affixed to the housing, or “can,” that encloses the x-ray tube assembly.
  • these attachments are accomplished by way of a weld or braze joint.
  • these joints have been implemented in a manner that is especially vulnerable to the thermal and mechanical stresses present, and often fail prematurely.
  • efficient removal of heat, as well as robust joint attachments between component parts is critical to maintaining structural integrity and increased operating life of the x-ray device.
  • a cooling system that can be used to efficiently and effectively remove heat from the x-ray tube, and especially in the areas of the cathode cylinder and the adjacent shield structure.
  • the system should prevent heat-related damage from occurring in the materials used to fabricate the cathode cylinder and shield assembly, and should reduce structural damage from occurring between joints and/or attachment points between the various structural components. Joints between components should be more robust, and able to withstand high temperatures.
  • a related objective of the present invention is to provide a cooling system that reduces temperature levels present within x-ray tube components and the coolant, thereby reducing the incidence of failure within the x-ray tube due to thermal stresses and increasing the overall operating life of the x-ray tube.
  • Another objective of the present invention to provide an improved x-ray tube cooling system in which coolant is circulated through passages formed within a shield structure so as to more efficiently remove heat by convection from the shield.
  • Yet another object of the present invention to provide an improved x-ray tube cooling system which utilizes a shield structure that has increased external surface area in contact with the cooling system coolant, thereby improving the efficiency and rate at which heat is removed from the shield structure.
  • Still another objective of the present invention is to provide a cooling system in which areas of the shield structure that have a higher thermal content are cooled at a rate higher than those portions of the shield structure having a lower thermal content.
  • Another objective of the present invention is to provide improved brazed joints between structures of the x-ray tube that are better able to withstand the thermal and mechanical stresses present within an operating x-ray tube.
  • a preferred embodiment of the system includes a reservoir containing a liquid coolant that is continuously circulated by way of a heat exchanger device.
  • an x-ray tube Disposed within the coolant reservoir is an x-ray tube, which consists of a cathode cylinder having an electron source, such as a cathode head assembly, disposed therein.
  • the x-ray tube is also comprised of an evacuated housing that encloses an anode having a target surface capable of receiving electrons emitted by the electron source.
  • Disposed between the cathode cylinder and the x-ray tube housing is a shield structure.
  • the shield structure includes an aperture through which electrons are passed from the electron source to the target surface to generate x-rays.
  • the shield structure provides an electron collection surface, that prevents electrons that rebound from the target surface from re-striking the target.
  • At least one fluid passageway is formed within the shield structure.
  • the fluid passageway receives coolant from the reservoir from an inlet port, which then passes through the passageway so as to absorb heat generated in the shield structure, including heat generated as a result of rebounding electrons striking inner surfaces of the shield.
  • Preferred embodiments of the cooling system also include a plurality of extended surfaces, or cooling fins, that are affixed to the outer surface of the shield structure. Coolant exiting the fluid passageway is allowed to flow across the extended surfaces, which are oriented in a manner so as to conduct heat from the shield to the coolant.
  • the cooling system also includes means for augmenting the heat transfer capability of the fluid passageway.
  • this means is comprised of a coiled spring that is disposed within the fluid passageway. The spring provides an extended surface that increases the efficiency and rate at which heat is removed by convection from the shield structure.
  • the fluid passageways that are formed within the shield structure are oriented in a manner that permits coolant to flow through a first and a second section of the shield structure. Moreover, the passageways are further oriented such that the heat is transferred away from the first section at a greater rate than in the second section. In this way, those sections (i.e., the first section) having a higher thermal content are cooled at a faster rate than those sections (i.e., the second section) having a lower thermal content. This ensures a more efficient and evenly distributed dissipation of heat, and also helps ensure that the coolant is not overly thermally stressed.
  • Embodiments of the invention also are disclosed that provide a more structurally sound x-ray tube assembly, and that is thus better able to withstand the thermal and mechanical stresses present in an operating tube.
  • an improved braze joint is provided between the shield structure and the x-ray tube housing.
  • a braze material is placed along a joint formed along both a horizontal and a vertical surface of the shield structure and the x-ray tube housing. This ensures a connection joint that is more structurally sound, and that is able to survive the varying temperatures, and resultant stresses imposed during operation of the tube.
  • FIG. 1 is a plan view of one preferred embodiment of the cooling system
  • FIG. 2 is an isometric cross-section view of an embodiment of the cathode cylinder and finned shield structure depicted in FIG. 1;
  • FIG. 3 is an isometric view of one presently preferred embodiment of the shield structure
  • FIG. 4 is a side view of the shield structure in FIG. 3;
  • FIG. 5 is a plan view of the shield structure
  • FIG. 6 is a cross-sectional view of the shield structure depicted in FIG. 3;
  • FIG. 7 is a plan view of an alternative embodiment of the cooling system
  • FIG. 8 is an exploded perspective view of another presently preferred embodiment of a shield structure
  • FIG. 9A is a cross-sectional view of the assembled shield structure of FIG. 8;
  • FIG. 9B is a plan view of the shield structure of FIG. 8;
  • FIG. 10 is a cross-sectional view of a cathode cylinder, shield structure and x-ray tube can assembly
  • FIG. 11 is a detail view taken along lines 11 — 11 in FIG. 10, showing the braze joint configuration between the aperture disk and the x-ray tube can;
  • FIG. 12A is a schematic representation illustrating the fluid flow through the lower half of the shield structure.
  • FIG. 12B is a schematic representation illustrating an alternative arrangement for fluid flow through the lower half of the shield structure.
  • An x-ray tube designated generally at 101 , is formed generally with an evacuated envelope housing that is typically referred to as a “can” 107 .
  • the evacuated envelope, or can, 107 is disposed within a housing 112 .
  • an electron source in the form of a cathode head 106 , filament (not shown) and associated electronics (not shown), that is disposed within a cathode cylinder 102 .
  • a electron collection device Adjacent to the cathode 106 , and attached to the end of cathode cylinder 102 , is a electron collection device, sometimes referred to as an “aperture,” and referred to herein as a shield structure 108 .
  • a rotating target anode 104 is disposed within the x-ray tube 101 .
  • a voltage source is connected to the anode and the cathode, and electrons emitted by the cathode 106 are accelerated when a voltage difference is applied between the cathode and anode. As the high velocity electrons stream towards the anode, they pass through an aperture 122 formed within the shield structure 108 .
  • x-rays When the electrons impact the surface of the target anode 104 , a portion of the kinetic energy is converted to x-rays. These x-rays arc then partially collimated and emitted through a window 103 (FIG. 1) formed in the side of the x-ray tube 101 , and a corresponding window in the housing 112 (not shown).
  • some of the electrons that strike the target anode surface 104 are not converted into x-rays. Instead, they may rebound from the target anode 104 .
  • the shield structure 108 functions so as to prevent the rebounding electrons from descending and re-striking the target anode 104 —and thereby generating off-focus x-rays. In addition, some of the rebounding electrons will strike the inner surface of the cathode cylinder 102 .
  • FIG. 1 illustrates how in one presently preferred embodiment, the x-ray tube 101 is completely immersed within a liquid coolant 114 that is disposed within the reservoir formed by the housing 112 .
  • the coolant is re-circulated though the housing 112 via a pump/cooling unit 134 .
  • heat is dissipated from the x-ray tube components and absorbed by the coolant.
  • Heated coolant is then circulated to the heat exchanger 134 , where heat is removed by any appropriate means, such as a radiative surface or the like.
  • the cooled liquid is then re-circulated back to the housing reservoir.
  • the rate of heat transfer is proportional to the surface area across which the heat is transferred.
  • the efficiency at which heat is conducted from the x-ray tube to the coolant is based partly upon the surface area of the component being cooled, which in the past has been limited—especially in the problematic areas of the shield structure and the cathode cylinder 102 .
  • Embodiments of the present invention address this problem by way of the shield structure 108 , a preferred embodiment of which is shown generally in FIG. 1, and in further detail in FIGS. 2, 3 , 4 and 6 . As is shown in FIGS.
  • the shield structure 108 interconnects the main body portion of the evacuated envelope can 107 of the x-ray tube 101 with the cathode cylinder 102 .
  • the shield structure 108 includes a separate bottom cover, referred to as the aperture disk 137 (shown in FIGS. 2 and 8 ), that is affixed to the bottom of the shield 108 .
  • the disk 137 is in turn affixed to a corresponding recess 155 formed within the can 107 .
  • the attachment is accomplished with a braze joint, which is described in further detail below.
  • the shield 108 and the aperture disk 137 are each constructed of a aluminum oxide dispersion strengthened copper alloy, such as the material known by the tradename Glidcop AL-15 UNS C-15715 and sold by OMG Americas Inc. Other materials could also be used, including but not limited to Glidcop AL-25, and Glidcop AL-60 UNS C-15725 and UNS C-15760 respectively.
  • the shield structure 108 As is best seen in FIGS. 2 and 3, the shield structure 108 , as well as the aperture disk 137 , has an aperture or opening 122 that allows the electron stream to pass from the cathode 106 to the target anode 104 (FIG. 2 ). Also, disposed about the aperture 122 is a rebounding electron collection surface 124 , which provides the function of preventing rebounding electrons from descending and re-striking the target anode 104 .
  • the electron collection surface 124 is shaped and oriented in a manner such that the trajectory of rebounding electrons will cause them to strike the collection surface 124 instead of returning to the anode target surface 104 . In the illustrated embodiment, the surface 124 is sloped towards the aperture 122 with a concave shape. It will be appreciated that other shapes and contours could be used.
  • the shield structure includes a means for transferring heat away from the shield structure.
  • the heat transfer means is comprised of a plurality of cooling members or “fins,” which are designated at 110 in FIG. 1 and are shown in further detail in FIGS. 2, 3 , 4 and 6 .
  • These cooling fins 110 are comprised of adjacent annular extended surfaces formed about the periphery of the outer surface of the shield structure 108 , and are at least partially exposed to the reservoir coolant 114 , as is indicated in FIG. 1 .
  • the fins 110 effectively increase the amount of surface area of the shield 108 that is in contact with the reservoir coolant, and they thereby function to increase the efficiency and rate at which heat is conducted and transferred from the shield to the coolant.
  • This can best be seen in the perspective view of a preferred shield structure 108 in FIG. 3, and in the side elevation view of FIG. 4 .
  • the plurality of cooling fins I 10 are formed about the entire outer surface of the shield 108 , and are spaced apart so as to permit coolant to flow between the fins and thereby maximize the surface area exposed to the coolant. In this way, heat generated at the collection surface 124 , the inner surface 125 of the shield, or at the inner surface 109 (FIG.
  • the fins 110 are particularly useful in facilitating heat transfer by convection from the areas of the shield structure 108 and the cathode cylinder 102 to the coolant 114 , thereby reducing the damaging thermal effects of the rebounding electrons.
  • the enhanced cooling effect provided by the fins improves the operational life of the x-ray tube in other ways.
  • the fins 110 By conducting relatively more of the shield structure 108 heat to the coolant, the fins 110 reduce the heat load imposed on the coolant that is circulated through coolant passages formed in the shield (described below). In other words, the fins 110 serve to more efficiently redistribute the heat conducted from the shield structure 108 .
  • the cooling effect produced by the fins results in a reduction of about 7 percent to about 9 percent in the heat load imposed on the circulating coolant. Because the heat load on the circulating coolant is reduced, the circulating coolant is substantially less likely to experience thermal breakdown. The benefit is a longer lasting and more reliable x-ray tube device.
  • a preferred embodiment of this invention employs fins to increase the overall rate of heat transfer from the shield structure, and thus from the x-ray tube, it is recognized that an increase in the surface area by use of alternative structures or elements of the exposed surfaces of the shield can be used to cause a rise in the rate at which heat is transferred to the reservoir coolant.
  • cooling fins integral with the shield structure represent a preferred embodiment, this invention also contemplates discrete cooling fins, or a cooling fin structure that is separately attachable to the shield structure and/or the cathode cylinder, or similar arrangements.
  • the cooling system of the present invention also includes additional fluid passageways that are placed substantially proximate to the sources of heat, and which thereby function so as to further assist in the removal of heat generated within the x-ray tube during operation—especially in the area of the shield structure 108 .
  • these internal fluid passageways denoted at 131 and 132 in FIG. 2, are formed in two ways. First, a plurality of passageways 131 are formed in the bottom half section of the shield structure 108 .
  • passageways 131 can be formed directly and integrally within the body of the shield 108 (i.e., in the form of a hollow bore), or, as is the case with the illustrated embodiment, can be formed by forming channels with spaced apart ridges 133 and 135 in the bottom of the shield 108 (FIGS. 5 and 6 ).
  • a separate bottom cover referred to as the aperture disk 137
  • the aperture disk 137 is then affixed, preferably via a braze joint (an embodiment of which is described below), to a recess 155 formed in the can 107 .
  • the aperture disk 137 has a corresponding aperture 122 , as well as complementary ridges, designated at 133 ′ and 135 ′ in FIG. 2 (also shown in FIG. 8 ), that abut against the ridges 133 , 135 on shield 108 , thereby forming the passageways 131 when the disk 137 is mated with the shield 108 .
  • both fluid passageways labeled as 131 are in fluid communication with one another by virtue of gaps formed in circular ridge 135 , as is illustrated in FIG. 5 (also shown in FIG. 8 ).
  • a second set of passageways 132 are formed around the outer periphery of the shield 108 . These are formed with a plurality of spaced apart cooling surfaces 126 , also in the form of ridges, that, when inserted within the recess 155 of can 107 /manifold 116 abut against the inner surface of the recess 155 and thereby form individual passageways 132 .
  • FIG. 3 illustrates how each of the passageways 132 are in fluid communication with one another due to gaps 141 formed between adjacent ridges 126 .
  • the passageways 131 and 132 are placed in fluid communication with one another in a manner described below. As will also be described in further detail, during operation of the x-ray tube, coolant is recirculated throughout these passageways so as to remove heat by convection from the shield structure 108 .
  • the coolant 114 is supplied to the housing 112 via a conduit 105 disposed within the housing 112 reservoir.
  • the conduit 105 is connected to a manifold inlet/outlet connection 118 that is affixed, or formed integrally with, a coolant manifold 116 that is disposed on, or formed as an integral part of, the evacuated housing 107 of the x-ray tube 101 .
  • the coolant manifold 116 forms a fluid communication path between the inlet conduit 105 and the fluid passageways 131 via an inlet port hole formed in the manifold (not shown).
  • this is done by orienting the shield 108 within the manifold 116 such that a gap 151 / 151 ′ formed in abutting ridges 133 / 133 ′ is aligned with the inlet port hole so as to receive incoming coolant from inlet conduit 105 . Coolant is thus allowed to flow into passageways 131 . As the coolant enters passageway 131 , it splits into two flows, where each flow circulates in opposing azimuthal directions. Of course, as the coolant proceeds through the passageway 131 , heat is transferred to the coolant from the shield structure.
  • passageway 131 is placed in fluid communication with passageway 132 . This is accomplished by providing another gap 153 (FIG. 5) in ridge 133 at a point opposite to gap 151 (as well as corresponding gaps in the aperture disk, shown in FIG. 8 ).
  • a cavity (designated in FIGS. 12A and 12B at 200 ) is formed within the interior wall of recess 155 . This cavity 200 is aligned with the gap 153 , and is sufficiently large so as to place passageway 131 in fluid communication with at least one of the passageways 132 .
  • two coolant flows proceed through passageway 131 and then converge at the opposite side of the shield 108 .
  • the coolant then continues to flow into the cavity 200 via gap 153 / 153 ′, and then into the upper half of the shield 108 via the passageways 132 . Again, the coolant splits and the two flows traverse the upper half of the shield 108 . Also, as in the lower half, the coolant is heated as it flows over the shield and the surfaces 126 .
  • manifold inlet/outlet connection 118 is also formed within manifold inlet/outlet connection 118 .
  • outlet port hole (not shown) that is in fluid communication with passageway 132 .
  • the two flows of coolant traverse the upper half of shield 108 the flows converge and then exit at the outlet port hole, which is in fluid communication with an outlet conduit 120 .
  • the outlet conduit is in fluid communication with the reservoir, as is indicated by the fluid flow line.
  • another manifold may be used to direct the coolant to other cooling passages formed within other areas of the x-ray tube to effect additional heat removal by convection, before being discharged into the reservoir.
  • the coolant flows over the external surfaces of the x-ray tube, including the fin surfaces of the shield 108 as previously described, and cools by convection.
  • the coolant exits the reservoir 112 at reservoir discharge connection 136 , and flows back to the external heat exchanger to repeat the cycle, as is illustrated in FIG. 1 .
  • the convective heat transfer effected by the fins 110 complements the heat transfer achieved through convective cooling in the coolant passages 131 , 132 , and thus serves provides a relative increase in the overall rate of heat transfer from the shield structure 108 .
  • the relative orientation of the fluid inlet port from the manifold 116 to the passageways 131 in the lower half of the shield 108 may be varied.
  • the fluid inlet port ( 202 in FIG. 12A) is positioned directly opposite to, i.e., along a 180 degree angle, the point at which the coolant enters the upper half of the shield 108 and passageways 132 .
  • This flow scheme is schematically represented in FIG. 12A, where coolant enters the lower half of the shield 108 via inlet port 202 , then splits into two flows that each circulate in opposing azimuthal directions. The two flows then converge at the cavity 200 , where it enters the upper half of the shield 108 via passageways 132 .
  • the flow rate of the two flows is approximately equal, and thus the rate of heat transfer is approximately equal.
  • heat within the shield 108 is non-uniform. Namely, the side of the shield that is more proximate to the x-ray window 103 is typically subjected to higher temperatures than the opposite side. This is due to the effect imposed by the target angle on the back scattered electrons, i.e., more electrons hit the window side of the electron collection surface 124 than the centerline side. As such, in another preferred embodiment, the flow rate is increased in that portion of the shield having a higher thermal content (i.e., the side more proximate to the window 103 ), which thereby increases the rate of heat removal. In one embodiment, the is accomplished by varying the relative orientation of the inlet port 202 with respect to the passageways 131 .
  • FIG. 12 B This particular arrangement is represented in FIG. 12 B.
  • an angle ⁇ of less than 180 degrees is used to orient the inlet port 202 with the passageway 131 and the cavity 200 on the side proximate to the x-ray window 103 .
  • This decrease in relative travel distance increases the coolant flow rate, thereby increasing the convective heat transfer coefficient on that side and decreasing the shield's temperature gradient in the azimuthal direction. Consequently, the heat transfer rate on the window side is increased. Conversely, the heat transfer is decreased on the remaining side of the shield 108 .
  • Increasing the rate of heat transfer can be accomplished with other approaches as well. For instance, in the side proximate to the window 103 (or whatever portion has higher thermal content), the flow area cross section of the passageway 131 could be increased, and the passageway disposed in the opposite/remaining portion of the shield decreased. This would increase the volume of coolant flow through the portion of the shield having a higher thermal content, and thus increase the rate of heat transferred by convection.
  • FIG. 7 illustrates a presently preferred alternative embodiment of a cooling system.
  • the coolant manifold 116 operates in conjunction with external fins 110 to facilitate an enhanced convective cooling of the shield structure 108 , and thus, of the x-ray tube 100 as a whole.
  • a coolant flow is generated by a cooling unit 134 as previously described, and coolant flows through inlet conduit 105 , into the coolant manifold 116 , and into passageways 131 and 132 in the manner previously described.
  • the output conduit 120 is connected to a flow diverter, designated at 128 , which splits the coolant into two discharge streams.
  • coolant outlet port 138 One of the coolant streams from the flow diverter 128 is discharged to the reservoir 112 through coolant outlet port 138 (or, optionally, into another manifold where it can be directed to other areas of the x-ray tube, as previously noted).
  • the other coolant stream from the flow diverter 128 is discharged through coolant outlet port 130 and the flow is specifically directed across fins 110 . This directed flow more efficiently removes heat from the fins 110 .
  • the coolant eventually exits the reservoir at the reservoir discharge connection 136 and flows back to the cooling unit 134 to repeat the cycle.
  • the alternative embodiment of FIG. 7 enhances cooling of the x-ray tube by: i) providing cooling fins 110 to increase the surface area of the x-ray tube, and in particular the shield 108 , thereby increasing the rate of convective heat transfer from the x-ray tube structures to the reservoir coolant; ii) directing a portion of the manifold coolant discharge across the fins to increase convective heat transfer from the fins, thus augmenting the convective cooling effect of the fins; and iii) convectively cooling the interior of the shield structure.
  • the combined effect of the internal cooling passages, external fins, and dual discharge manifold is to significantly increase the rate at which heat is removed from the x-ray tube.
  • the enhanced heat transfer rate serves to reduce x-ray tube operating temperatures and thus the resultant thermal mechanical stresses, and substantially prevents thermal breakdown of the coolant, thereby extending the life of the coolant and, accordingly, the x-ray tube.
  • FIGS. 8 and 9 A- 9 B illustrate another embodiment of a shield structure, designated generally at 108 ′.
  • the shield 108 ′ is similar to the shield 108 described previously, and the discussion for like elements will not be repeated.
  • the aperture disk 137 along with ridges 133 ′ and 135 ′ that mate with corresponding ridges 133 and 135 formed on the bottom of shield 108 ′ so as to form fluid passageway 131 .
  • the embodiment of FIG. 8 differs from that of FIGS. 1-7 in one primary respect.
  • the shield assembly 108 ′ includes means for augmenting the heat transfer capability of the coolant passageway.
  • one structure for performing this function is a coiled wire, designated in FIG.
  • FIG. 9A illustrates the coiled wires 300 , 302 disposed within the fluid passageways 131 .
  • the coiled wires 300 , 302 are comprised of a thermally conductive material material, such as copper or an aluminum oxide dispersion strengthened copper alloy of the sort used in the shield.
  • Each turn of the coiled wire can have either a circular or noncircular cross section and, optionally, can have non-uniform diameter/thickness.
  • Turns of the coiled wire can be secured to the interior wall of the fluid passageway by brazing, or similar attachment means, which also can increase thermal conduction.
  • Each coil augments the heat transfer rate provided by coolant within the passageway 131 .
  • the presence of the coiled wire adds additional surface area within the passageway, which thereby facilitates the transfer of heat.
  • the coil breaks the boundary layers of coolant as the coolant passes over the coils within the passageway. This promotes turbulence, and further improves heat transfer.
  • coolant flows both parallel and perpendicular to the axes of the coil wires 300 , 302 . This further increases the rate and efficiency at which heat is transferred away from the shield 108 ′.
  • FIGS. 10 and 11 Preferred embodiments of this brazing arrangement are shown in FIGS. 10 and 11, to which reference is now made.
  • FIG. 10 is a simplified view of a cathode cylinder 102 affixed to a shield 108 and aperture disk 137 assembly, which is in turn affixed to the x-ray tube can 107 .
  • FIG. 11 is an exploded view taken along lines 11 — 11 in FIG. 10, which illustrates one presently preferred embodiment of the braze joint between the can 137 and the aperture disk 137 .
  • the aperture disk 137 includes a shoulder region 350 that projects outwardly around the disk 137 periphery.
  • the can 107 includes a correspondingly shaped shoulder region 352 that mates with that of the disk 137 .
  • the two shoulder regions together form a horizontal mating region at 402 , as well as a vertical mating region 400 .
  • These two regions can be brazed together.
  • the arrangement is particularly advantageous in that it decreases the stresses between the disk 137 and the can 107 by factors of six or more in preferred embodiments, when compared to joint arrangements having a braze only along a horizontal surface.
  • the improved braze joint better resists stresses associated with the extreme temperatures of the x-ray tube, resulting in a device that is less subject to failure and that provides a longer overall operational life.

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  • X-Ray Techniques (AREA)
US09/351,579 1999-07-12 1999-07-12 X-ray tube cooling system Expired - Lifetime US6400799B1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US09/351,579 US6400799B1 (en) 1999-07-12 1999-07-12 X-ray tube cooling system
PCT/US2000/018796 WO2001005196A2 (en) 1999-07-12 2000-07-10 X-ray tube cooling system
DE60045160T DE60045160D1 (de) 1999-07-12 2000-07-10 Kühlanlage für röntgenstrahlröhre
EP00948608A EP1234320B1 (en) 1999-07-12 2000-07-10 X-ray tube cooling system
JP2001510277A JP4376480B2 (ja) 1999-07-12 2000-07-10 Ｘ線管冷却システム
US09/656,076 US6519318B1 (en) 1999-07-12 2000-09-07 Large surface area x-ray tube shield structure
JP2008248952A JP4749456B2 (ja) 1999-07-12 2008-09-26 Ｘ線管冷却システム及びｘ線管生成装置

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US09/351,579 US6400799B1 (en) 1999-07-12 1999-07-12 X-ray tube cooling system

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Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6993116B1 (en) * 2003-10-17 2006-01-31 Siemens Aktiengesellschaft Metallic vacuum housing for an X-ray tube
US20060050850A1 (en) * 2004-09-03 2006-03-09 Varian Medical Systems Technologies, Inc. Shield structure and focal spot control assembly for x-ray device
US20060228238A1 (en) * 2005-04-06 2006-10-12 Andrews Gregory C Coolant pump for x-ray device
US20060269048A1 (en) * 2005-05-25 2006-11-30 Cain Bruce A Removable aperture cooling structure for an X-ray tube
US20060274891A1 (en) * 2005-06-01 2006-12-07 Endicott Interconnect Technologies, Inc. Imaging inspection apparatus with improved cooling
WO2006029026A3 (en) * 2004-09-03 2006-12-14 Varian Med Sys Tech Inc Shield structure and focal spot control assembly for x-ray device
US20070009084A1 (en) * 2005-06-01 2007-01-11 Endicott Interconnect Technologies, Inc. Imaging inspection apparatus with directional cooling
US20070140431A1 (en) * 2005-12-19 2007-06-21 Miller Robert S Shielded cathode assembly
US20070140432A1 (en) * 2005-12-20 2007-06-21 General Electric Company Structure for collecting scattered electrons
US20080095317A1 (en) * 2006-10-17 2008-04-24 General Electric Company Method and apparatus for focusing and deflecting the electron beam of an x-ray device
US20080112540A1 (en) * 2006-11-09 2008-05-15 General Electric Company Shield assembly apparatus for an x-ray device
US20080112538A1 (en) * 2006-11-09 2008-05-15 General Electric Company Electron absorption apparatus for an x-ray device
US20080310596A1 (en) * 2004-06-30 2008-12-18 Koninklijke Philips Electronics, N.V. X-Ray Tube Cooling Apparatus
US20090052627A1 (en) * 2005-12-20 2009-02-26 General Electric Company System and method for collecting backscattered electrons in an x-ray tube
US20090080617A1 (en) * 2007-09-25 2009-03-26 Varian Medical Systems Technologies, Inc. Aperture shield incorporating refractory materials
US20100278309A1 (en) * 2007-12-19 2010-11-04 Koninklijke Philips Electronics N.V. Scattered electron collector
US20120114104A1 (en) * 2010-11-09 2012-05-10 Varian Medical Systems, Inc. Asymmetric x-ray tube
US20130083896A1 (en) * 2011-10-04 2013-04-04 Takashi Watanabe Apparatus, x-ray irradiation method, and structure manufacturing method
KR101283935B1 (ko) 2011-11-21 2013-07-16 강릉원주대학교산학협력단 냉각기능을 갖는 수중물체
RU2509389C1 (ru) * 2012-07-30 2014-03-10 Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" - Госкорпорация "Росатом" Источник мягкого рентгеновского излучения на основе разборной рентгеновской трубки
WO2015077330A3 (en) * 2013-11-19 2015-11-12 Varian Medical Systems, Inc. High power x-ray tube housing
WO2015077322A3 (en) * 2013-11-19 2015-11-19 Varian Medical Systems, Inc. X-ray housing having integrated oil-to-air heat exchanger
US20210305003A1 (en) * 2020-03-31 2021-09-30 Energetiq Technology, Inc. X-ray generation apparatus
WO2022023695A1 (en) * 2020-07-27 2022-02-03 Aquasium Technology Limited Electron beam welding apparatus
CN116033639A (zh) * 2023-02-15 2023-04-28 上海超群检测科技股份有限公司 X射线源的内置式液冷循环系统

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6457859B1 (en) * 2000-10-18 2002-10-01 Koninklijke Philips Electronics Nv Integration of cooling jacket and flow baffles on metal frame inserts of x-ray tubes
CN1910968B (zh) * 2004-01-13 2010-11-03 皇家飞利浦电子股份有限公司 X射线管的冷却装置和冷却方法以及x射线管组件

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5541975A (en) * 1994-01-07 1996-07-30 Anderson; Weston A. X-ray tube having rotary anode cooled with high thermal conductivity fluid
US5689542A (en) * 1996-06-06 1997-11-18 Varian Associates, Inc. X-ray generating apparatus with a heat transfer device
US6115454A (en) * 1997-08-06 2000-09-05 Varian Medical Systems, Inc. High-performance X-ray generating apparatus with improved cooling system

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1036406B (de) * 1955-05-04 1958-08-14 Max Planck Gesellschaft Roentgenroehre
US4309637A (en) * 1979-11-13 1982-01-05 Emi Limited Rotating anode X-ray tube
JPS59128198A (ja) * 1983-01-07 1984-07-24 新立川航空機株式会社 車両昇降装置における車両受台の昇降駆動装置
US4625324A (en) * 1983-09-19 1986-11-25 Technicare Corporation High vacuum rotating anode x-ray tube
US4945562A (en) * 1989-04-24 1990-07-31 General Electric Company X-ray target cooling

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5541975A (en) * 1994-01-07 1996-07-30 Anderson; Weston A. X-ray tube having rotary anode cooled with high thermal conductivity fluid
US5689542A (en) * 1996-06-06 1997-11-18 Varian Associates, Inc. X-ray generating apparatus with a heat transfer device
US6115454A (en) * 1997-08-06 2000-09-05 Varian Medical Systems, Inc. High-performance X-ray generating apparatus with improved cooling system

Cited By (46)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6993116B1 (en) * 2003-10-17 2006-01-31 Siemens Aktiengesellschaft Metallic vacuum housing for an X-ray tube
US7839980B2 (en) * 2004-06-30 2010-11-23 Koninklijke Philips Electronics N.V. X-ray tube cooling apparatus
US20080310596A1 (en) * 2004-06-30 2008-12-18 Koninklijke Philips Electronics, N.V. X-Ray Tube Cooling Apparatus
US7289603B2 (en) * 2004-09-03 2007-10-30 Varian Medical Systems Technologies, Inc. Shield structure and focal spot control assembly for x-ray device
US20060050850A1 (en) * 2004-09-03 2006-03-09 Varian Medical Systems Technologies, Inc. Shield structure and focal spot control assembly for x-ray device
WO2006029026A3 (en) * 2004-09-03 2006-12-14 Varian Med Sys Tech Inc Shield structure and focal spot control assembly for x-ray device
US20060228238A1 (en) * 2005-04-06 2006-10-12 Andrews Gregory C Coolant pump for x-ray device
US20060269048A1 (en) * 2005-05-25 2006-11-30 Cain Bruce A Removable aperture cooling structure for an X-ray tube
US7486774B2 (en) * 2005-05-25 2009-02-03 Varian Medical Systems, Inc. Removable aperture cooling structure for an X-ray tube
US20070009084A1 (en) * 2005-06-01 2007-01-11 Endicott Interconnect Technologies, Inc. Imaging inspection apparatus with directional cooling
US7261466B2 (en) 2005-06-01 2007-08-28 Endicott Interconnect Technologies, Inc. Imaging inspection apparatus with directional cooling
US7354197B2 (en) 2005-06-01 2008-04-08 Endicott Interconnect Technologies, Inc. Imaging inspection apparatus with improved cooling
US7510324B2 (en) 2005-06-01 2009-03-31 Endicott Interconnect Technologies, Inc. Method of inspecting articles using imaging inspection apparatus with directional cooling
US20060274891A1 (en) * 2005-06-01 2006-12-07 Endicott Interconnect Technologies, Inc. Imaging inspection apparatus with improved cooling
US7490984B2 (en) 2005-06-01 2009-02-17 Endicott Interconnect Technologies, Inc. Method of making an imaging inspection apparatus with improved cooling
US20080170670A1 (en) * 2005-06-01 2008-07-17 Endicott Interconnect Technologies , Inc. Method of inspecting articles using imaging inspection apparatus with directional cooling
US7661445B2 (en) * 2005-12-19 2010-02-16 Varian Medical Systems, Inc. Shielded cathode assembly
US20070140431A1 (en) * 2005-12-19 2007-06-21 Miller Robert S Shielded cathode assembly
US20070140432A1 (en) * 2005-12-20 2007-06-21 General Electric Company Structure for collecting scattered electrons
US20090052627A1 (en) * 2005-12-20 2009-02-26 General Electric Company System and method for collecting backscattered electrons in an x-ray tube
US7359486B2 (en) * 2005-12-20 2008-04-15 General Electric Co. Structure for collecting scattered electrons
US7668298B2 (en) * 2005-12-20 2010-02-23 General Electric Co. System and method for collecting backscattered electrons in an x-ray tube
US20080095317A1 (en) * 2006-10-17 2008-04-24 General Electric Company Method and apparatus for focusing and deflecting the electron beam of an x-ray device
US7410296B2 (en) 2006-11-09 2008-08-12 General Electric Company Electron absorption apparatus for an x-ray device
US20080112538A1 (en) * 2006-11-09 2008-05-15 General Electric Company Electron absorption apparatus for an x-ray device
US20080112540A1 (en) * 2006-11-09 2008-05-15 General Electric Company Shield assembly apparatus for an x-ray device
US20090080617A1 (en) * 2007-09-25 2009-03-26 Varian Medical Systems Technologies, Inc. Aperture shield incorporating refractory materials
US8000450B2 (en) * 2007-09-25 2011-08-16 Varian Medical Systems, Inc. Aperture shield incorporating refractory materials
US8233589B2 (en) * 2007-12-19 2012-07-31 Koninklijke Philips Electronics Nv Scattered electron collector
US20100278309A1 (en) * 2007-12-19 2010-11-04 Koninklijke Philips Electronics N.V. Scattered electron collector
US20120114104A1 (en) * 2010-11-09 2012-05-10 Varian Medical Systems, Inc. Asymmetric x-ray tube
US8867706B2 (en) * 2010-11-09 2014-10-21 Varian Medical Systems, Inc. Asymmetric x-ray tube
US9234855B2 (en) * 2011-10-04 2016-01-12 Nikon Corporation Apparatus, X-ray irradiation method, and structure manufacturing method
US20130083896A1 (en) * 2011-10-04 2013-04-04 Takashi Watanabe Apparatus, x-ray irradiation method, and structure manufacturing method
KR101283935B1 (ko) 2011-11-21 2013-07-16 강릉원주대학교산학협력단 냉각기능을 갖는 수중물체
RU2509389C1 (ru) * 2012-07-30 2014-03-10 Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" - Госкорпорация "Росатом" Источник мягкого рентгеновского излучения на основе разборной рентгеновской трубки
WO2015077330A3 (en) * 2013-11-19 2015-11-12 Varian Medical Systems, Inc. High power x-ray tube housing
WO2015077322A3 (en) * 2013-11-19 2015-11-19 Varian Medical Systems, Inc. X-ray housing having integrated oil-to-air heat exchanger
CN105874294A (zh) * 2013-11-19 2016-08-17 瓦里安医疗系统公司 具有集成的油-空气热交换器的x射线外壳
US9648710B2 (en) 2013-11-19 2017-05-09 Varex Imaging Corporation High power X-ray tube housing
US9717137B2 (en) 2013-11-19 2017-07-25 Varex Imaging Corporation X-ray housing having integrated oil-to-air heat exchanger
US20210305003A1 (en) * 2020-03-31 2021-09-30 Energetiq Technology, Inc. X-ray generation apparatus
US11164713B2 (en) * 2020-03-31 2021-11-02 Energetiq Technology, Inc. X-ray generation apparatus
WO2022023695A1 (en) * 2020-07-27 2022-02-03 Aquasium Technology Limited Electron beam welding apparatus
CN116033639A (zh) * 2023-02-15 2023-04-28 上海超群检测科技股份有限公司 X射线源的内置式液冷循环系统
CN116033639B (zh) * 2023-02-15 2024-04-05 上海超群检测科技股份有限公司 X射线源的内置式液冷循环系统

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EP1234320A2 (en) 2002-08-28
JP2009009953A (ja) 2009-01-15
JP4376480B2 (ja) 2009-12-02
WO2001005196A2 (en) 2001-01-18
JP4749456B2 (ja) 2011-08-17
EP1234320B1 (en) 2010-10-27
JP2003506817A (ja) 2003-02-18
DE60045160D1 (de) 2010-12-09
WO2001005196A3 (en) 2002-06-27
EP1234320A4 (en) 2006-07-19

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